Climate parameters have a decisive influence on the thermal reliability of the enclosing structures. A sufficient level of thermal reliability is ensured by the correct choice of the heat transfer resistance of the enclosures, taking into account the statistical characteristics of the atmospheric air temperature in the construction area. Objective indicators of thermal reliability are considered to be the absolute and relative duration of the thermal failure state according to the criteria of comfort in the room and the formation of condensate on the inner surface of enclosures. According to the results of thermal failures duration estimation of walls of residential buildings with different heat transfer resistance in different climate conditions, it was found that condensation on flat areas of walls is extremely unlikely, which should be analysed only for areas of high heat transfer in enclosing structures. The method of choosing the heat transfer resistance of the walls of civil buildings is developed. According to a given level of thermal reliability it takes into account the random nature of the size of structure, thermal characteristics of materials, indoor and outdoor air temperatures. The calculation examples of walls of residential buildings in essentially different climate conditions are performed. The developed technique allows to establish the heat transfer resistance of the enclosing structure, which provides a given duration of thermal failure state.